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USBMIDI

Table of Contents

  1. Hello World
  2. API
  3. More example
  4. Related

mbed OS 2 and mbed OS 5

This is the handbook for mbed OS 2. If you’re working with mbed OS 5, please see the new handbook and API References.

The USBMIDI interface can be used to send and receive MIDI messages over USB using the standard USB-MIDI protocol.

Using this library, you can do things like send MIDI messages to a computer (such as to record in a sequencer, or trigger a software synthesiser) and receive messages from a computer (such as actuate things based on MIDI events)

The USB connector should be attached to

  • p31 (D+), p32 (D-) and GND for the LPC1768 and the LPC11U24
  • The on-board USB connector of the FRDM-KL25Z

Hello World

Import program
USBMIDI_HelloWorld - main.cpp

00001 // Hello World example for the USBMIDI library
00002 
00003 #include "mbed.h"
00004 #include "USBMIDI.h"
00005 
00006 USBMIDI midi;
00007 
00008 int main() {             
00009     while (1) {    
00010         for(int i=48; i<83; i++) {     // send some messages!
00011             midi.write(MIDIMessage::NoteOn(i));
00012             wait(0.25);
00013             midi.write(MIDIMessage::NoteOff(i));
00014             wait(0.5);
00015         }
00016     }
00017 }

API

Import library
USBDevice - USBMIDI Class Reference

Public Member Functions

USBMIDI (uint16_t vendor_id=0x0700, uint16_t product_id=0x0101, uint16_t product_release=0x0001)
Constructor.
void write ( MIDIMessage m)
Send a MIDIMessage .
void attach (void(*fptr)( MIDIMessage ))
Attach a callback for when a MIDIEvent is received.

More example

In this example, you can control the MIDI message sent with buttons

Import program
USBMIDI_Receive - main.cpp

00001 // Hello World example for the USBMIDI library
00002 
00003 #include "mbed.h"
00004 #include "USBMIDI.h"
00005 
00006 //USBMIDI object
00007 USBMIDI midi;
00008 
00009 
00010 // Leds which will be switch on or off according to a MIDImessage
00011 BusOut leds(LED1, LED2, LED3, LED4);
00012 
00013 BusInOut buttons(p22, p23, p24, p25);
00014 
00015 void show_message(MIDIMessage msg) {
00016     switch (msg.type()) {
00017         case MIDIMessage::NoteOnType:
00018             switch (msg.key()) {
00019                 case 48:
00020                     leds = (1 << 0);
00021                     break;
00022                 case 49:
00023                     leds = (1 << 1);
00024                     break;
00025                 case 50:
00026                     leds = (1 << 2);
00027                     break;
00028                 case 51:
00029                     leds = (1 << 3);
00030                     break;
00031             }
00032             break;
00033         case MIDIMessage::NoteOffType:
00034         default:
00035             leds = 0;
00036     }
00037 }
00038 
00039 int main() {
00040     uint8_t bus = 0;
00041     uint8_t p_bus = 0;
00042 
00043     // call back for messages received
00044     midi.attach(show_message);
00045 
00046     while (1) {
00047 
00048         //if buttons state changes, send a MIDI message
00049         bus = buttons.read();
00050         for (int i = 0; i < 4; i++) {
00051             if ( (bus & (1 << i)) != (p_bus & (1 << i))) {
00052                 if (bus & (1 << i)) {
00053                     midi.write(MIDIMessage::NoteOn(48 + i));
00054                 } else if ( !(bus & (1 << i)) ) {
00055                     midi.write(MIDIMessage::NoteOff(48 + i));
00056                 }
00057 
00058             }
00059         }
00060         wait(0.001);
00061         p_bus = bus;
00062     }
00063 }
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